1. Field of the Invention
The present invention pertains to electronic miniature circuit breakers such as the arc fault circuit interrupter (AFCI), combination arc fault circuit interrupter (CAFCI), dual function (DF) arc fault interrupter/ground fault interrupter (AFCI/GFCI), and ground fault circuit interrupter (GFCI) types and particularly those which can determine, record and report the cause of an interruption of power to the load.
2. Discussion of Related Art
With an electronic miniature circuit breaker such as the dual function (AFCI/GFCI) type there are three basic modes for which power to the branch circuit is interrupted, with each mode having two subcategories: 1) electronic trip, due to the AFCI or GFCI function; 2) mechanical trip, due to high instantaneous overcurrent (magnetic) or a lower and slower overcurrent (thermal/bimetal); and 3) an “upstream close-down” event, where a) someone turns the circuit breaker off at the handle, i.e. a “handle turn off,” or b) a power interruption occurring upstream from the circuit breaker.
There is a recognized need in the art to establish and report the cause of power interruption to the load so that the operator can properly address the maintenance of the electric system. In an electronic circuit breaker as cited above, it will be appreciated that either or both the supply and return current paths are monitored, typically by Current Transformers (CTs), shunt resistors, or other sensing means to establish arc fault (AF) or ground fault (GF) current flow anomalies.
When AF or GF current anomalies occur, the electronics (microprocessor, analog detection circuit, etc.) of the circuit breaker will issue a trip signal to an actuator, e.g. a solenoid, to operate a movable contact and separate the contacts of the circuit breaker. This electronic trip signal, and the reason for it, can be recorded and later displayed to the operator. For example U.S. Pat. No. 8,737,033, to Parker et al., proposes to record the behavior of current through the breaker, check the electronic record, and if no AF/GF command is issued, check the history of the current profile to determine if one of the mechanical trip subcategories is indicated, and if not, assume an upstream close-down event happened; and then record and report the findings. This plan requires the digital resources for the recording and processing of the current profile to effectuate this scheme.